Liquid spray apparatus



' July 18, 1961 w. MQK. MARTIN LIQUID SPRAY APPARATUS Filed Jan. 3, 19552 Sheets-Sheet 1 INVENTOR MAL/AM Ala/f 44,4277

.Tial" TTORNE'YS W. M K. MARTIN LIQUID SPRAY APPARATUS July 18, 1961 2Sheets-Sheet 2 Filed Jan. 5, 1955 i. .4. T a INVENTOR MAL/AM Mc/f. M41?T/N ATTORNEYS United Stfl Patent 2,992,778 LIQUID SPRAY APPARATUSWilliam McK. Martin, 457 Virginia Ave., San Mateo, Calif. Filed Jan. 3,1955, Ser. No. 479,353 4 Claims. (Cl. 239-223) This invention relates toapparatus and a process for applying surface coatings, and is morespecifically directed towards apparatus and a method for applying alacquer or similar protective coating on the inner peripheral surface ofa hollow cylindrical article.

As is well known in the art, it is in many instances desirable and oftennecessary to provide a protective coating over the entire exposed innersurface of containers such ascans in which food is packaged as well aslarger units such as pails and metal drums. Usually, this coating is alacquer or enamel which is painted on the required surfaces .or sprayedthereon with conventional spraying equipment. No particular difiicultyis encountered in the application of the lacquer to the flat end wallsof the container as this operation may be readily performed eitherbefore or after attachment of the end walls to the cylindrical body.However, in applying the lacquer to the inner surface of the body, it ispreferable to perform such operation after the rolling and longitudinalseaming of the body so as to prevent cracking or rupture of the lacquerfilm or coating, and it will be .appreciated that the application of acoating to the inner .wallsof a tubular member presents difliculties notfound in applying such a coating to a flat surface or even to theexternal surface of a. cylindrical member if the latter was desired. 1 I

Furthermore, in using conventional spraying equipment, liquid is ejectedfrom a nozzle by a high velocity airstream withthe liquid droplets beingcarried bythe airjstream towards the surface to be painted. However, itis well understood that an air stream will not confine 'itself to itsoriginal cross-sectional form, but will leave the nozzlein a graduallydiverging shape. This spreading out of the air stream results in acertain proportion of the more finely dispersed droplets likewise movingoutwardly, and consequently only the larger and heavier droplets willcontinueon in a, substantially straight path to engage and be depositedon the surface. This typeof operation not only results in an irregularandinferior coating, but actually promotes the formation of, undesirableair pockets between the surface and coating or, in the coating itself. al a It is therefore anobject of the present invention to provide animproved apparatus and method for applying a lacquer orsimilar coatingto theinner surface of a cylindrical containerin which the coating willpossess uniform consistency and thickness over the entire surface areaand will be. free from undesirable entrapment of air Another objectofthe invention is toprovide a method .and apparatus of the typedescribedin whichcentrifugal force is utilized to project the liquid towards the,surface to be coated whereby the above mentioned disadvantagesaccompanying conventional air stream-spraying opera- .tions may beeliminated.

A further object of the invention is to provide apparatus of the abovecharacter which is simple in construction and operation and in which themethod utilized is' extremely elfic ie nt and adapted for massproduction .operations.

A s tillfurther object of my invention is to provide a 'ice vaporatmosphere whereby a more impervious air-free coating may be obtained.

The invention possesses other objects and features of advantage, some ofwhich, with the foregoing, will be set forth in the followingdescription of the preferred form of the invention which is illustratedin the drawing accompanying and forming part of the specification. It isto be understood, however, that variations in the showing made by thesaid drawing and description may be adopted within the scope of theinvention as set forth in the claims.

Referring to said drawing:

FIGURE 1 is a vertical view, mostly in section, of the novel apparatuswhich may be utilized in carrying out the method of the presentinvention, the apparatus being shown in operation on a cylindricalcontainer.

FIGURE 2 is an enlarged vertical cross-section view on an enlarged scaleof the rotor assembly.

FIGURE 3 is a cross-sectional view taken substantially in the planeindicated by line 3-3 of FIGURE 2.

FIGURE 4 is a diagrammatic view of a modifiedform of spray apparatus.

In broad terms, the method employed herein for coating the inner wallsof a cylindrical container comprises heating the lacquer or othercoating to a temperature above the boiling point of the solventcontained therein, casting droplets of the lacquer towards the surfaceto be sprayed by means of centrifugal force, and elfecting axialmovement between the lacquer spraying apparatus and the containerwhereby the entire length of the latter will be coated.

There are several reasons for heating the lacquer, and include areduction in the viscosity thereof so as to facilitate its breaking upinto droplets, and by raising the temperature to above the boiling pointof .the solvents in the lacquer, solvent vapors will be released andimpelled against the surface with the spray, and result in a scavengingor sweeping of all air from the surface on which the droplets aredeposited. In other words, there will be a vapor atmosphere on thesurface instead of air, thus precluding any undesirable entrapment ofair under the deposit of the lacquer film or coating. It will likewisebe appreciated that the initial evaporation of the solvents willmaterially reduce the time required for baking the coating in ovens orthe like, and it is believed that the deposit of a hot lacquer film willprovide a more impervious coating with a higher gloss. It should be madeclear that while the term lacquer may be extensively used throughoutthis specification, I do not mean to limit the coating to a shellac andalcohol composition, but the coating may consist of other varnishes,paints or the like.

As hereinabove discussed, certain disadvantages and short comings arisefrom the use of conventional spraying equipment in which a high velocityair stream is utilized to eject and carry the liquid to be sprayed.Accordingly, as a principal feature of this invention, a physical forceis imparted to the liquid so that the liquid droplets may be impelledagainst the surface to be coated without being carried in an air streamor jet. This force is preferably created by a high velocity rotor havingperipheral openings through which the liquid is cast, the rotating rotorsetting up a high centrifugal force on the liquid.

Further operational details will be discussed in connection with anexplanation of the apparatus disclosed in the accompanying drawings.Referring first to FIG- URE l, a drum or cylindrical container 12 havinga side wall and a bottom and an open top is shown in position to receivean inner surface coating of lacquer or the like. In view of the factthat the lacquer is to be sprayed, the container is preferably placedinto a cylindrical open top receptacle having side walls 13 and abottom14, such receptacle serving to prevent the hurling of lacquer outsidethe vicinity of the apparatus, and to trap excess lacquer for subsequentreuse.

Disposed medially of the walls 13 is a rotor 16 arranged to be rotatedaboutthe axis of the cylindrical receptacle. The rotor is designed toreceive a quantity of lacquer, and by providing the rotor periphery withsuitable openings, the centrifugal "force upon the liquid during rotorrotation will cause thelatter to leave the rotor tangentially and beimpelled against the side wall of the container 12 which encompasses therotor. As the force at which the liquid leaves the rotor will increasein proportion to the square of the rotor speed, by rotating the rotor inthe neighborhood of several thousand r.p.m., a substantial force iscreated which insures the liquid engaging the container wall. Theparticular speed will of course be determined with reference to thediameter of the rotor and the inner diameter of the article beingsprayed.

In practically all instances, the'width or vertical height of the liquidimpelled from the rotor will be substantially less than the height ofthe container being sprayed. Accordingly, during the spraying operation,there must be a relative axial movement between the rotor and containerso that all surface portions of the latter will be coated. This could bedone by axially moving the rotor along the length of the 'conta'inenbutthe necessary movement is now shown by moving the container relative to"the rotor. This may be easily accomplished by pro viding conventionalclamping mechanism 17 which usually includes -a center support element18 for attachment to an overhead crane hook or the like, links 19pivotal-1y secured thereto, links "21 pivotally mounted at the ends oflinks 19, and head or rim engaging hooks 22. This type of mechanism iswidely used for moving steel drums or the like, but it will beappreciated 'that any other means m ay 'be equally well used for'theforegoing purpose of moving the container in an axial path relative'tothe rotor '16.

Rotor16 may be cast or-otherwise formed to provide a downwardlydirected'hub 26'having a central bore 27 communicating withia'diametrically reduced counter-bore '28, and a radialflange'29extending normal to the hub axis. An upper centrally located boss "31having a threaded bore '30 is provided as a support for a cover plate"32, the *l-atter being held in position by a bolt or screw 33 inengagement with the boss bore 30. The flange '29 and'plate32, as will bemore fully explained hereinafter, cooperate to define a liquiddistribution chamber 34.

It is naturally desirable that the liquid be impelledin relatively smalldroplets rather than in a continuous stream, and accordingly means areprovided on the rotor for-breaking up the liquid into droplets foruniform dispersion and application to the container surface. As hereshown, such means comprise a band 36 having a 'plurality of smallperforations 37 over the area thereof positioned at'the peripheraloutlet of the cham'ber34. 7 The upper edge of the 'band may be securedto the plate 32 asby welding, and the'lower edge thereof may be seatedin a groove 38 provided on the upper surface of flange 29 when the plateis attached to the boss31. Preferably, 'a second perforated metal band39, mounted in the same manner as hand '36 is provided and positionedradially inwardly of the latter. By using the two bands in radiallyspaced relation, liquid in chamber 34 will be thoroughly dispersed intodroplets'hefore leaving the rotor. By way of example, the bands couldcomprise a metal screen having approximately a 20-50 mesh.

Additional means are also utilized for properly distributing the liquidentering the rotor chamber. As will be later explainedin more detail,the lacquer tank or supply communicates with chamber 34 throughcounterbore 28 andia plurality-of ports 41 extending fromthecounteribore upwardly and outwardly to emerge adjacent the lower endof boss 31. As the liquid emerges from the ports, it strikes a dishedsurface '42 of an annular bafiie 43, the latter being held in positionaround boss 31 by means of a radial shoulder 44 clamped between theupper end of the boss and plate 32. Flange 29 immediately subjacent thebafiie is provided with a concave portion 46. Thus, liquid enteringthrough ports 41 engages surface 42 and is swirled around'the latter toevenly distribute the liquid to all parts-0 f the chamber. The liquidwill actually connectin flange portion 46 from which it will enter thechamber.

Rotor 16 is mounted for rotation on a drive shaft 51 of hollowconstruction, the reason for such construction being to permit the flowof fluid therethrough as well as to permit a valve to be inserted tocontrol such 'fluid flow, these features being hereinafter explained "indetail. To avoid splashing of thelacquer on the shaft drive mechanism, Iprefer to position the latter exteriorly of the receptacle bottom '14.Thus, shaft 51 may pass through said bottom wall and be supported ona'bearing 52 depending from-such wall, while a suitable packing gland 53prevents leakage between the shaft and wall. The upper end of the shaftis inserted within and secured to hub 26 of the rotor and the lower endis provided with a sprocket'54 for connection to abelt 56, the latterbeing driven by a motor 57 through a motor sprocket 58. From theforegoing, it will be understood that while motor 57 is operating,rotation will be imparted to the rotor through shaft '51, and any liquidin rotor chamber '34 will be hurled outwardly by centrifugal force, anddiffused by passage through the multi-perforate band or hands beforestriking the container surface.

Lacquer is 'suppliedto chamber 34 from any suitable source, such as atank -60, and a pipe 62 connected to the bottom'wall 14'of the splashreceptacle may'serve to "divert excess lacquer accumulating in thelatter'to the tank. Mounted within the bore of drive shaft 51 is astationary sleeve'63through'which lacquer is introduced into the rotorchamber. The sleeve is preferably radially spaced from the inner surfaceof the drive shaft bore with bearings 64 disposed in such space, and"extends beyond the lower end of the shaft for connection to a feed pipe66 leading from tank 60. This connection may include a nipple 67provided radially on the sleeve and communicating with a radial borewhich intersects the main passage 68 of the sleeve. A pump 69,positionedin pipe '66 is utilized toinsure passageof liquid from the itanktoltherotor, and in order to heat the liquid *as it passes from the'tank tothe sleeve, a heat exchanger 61 is provided in the feedpipe 66.

The upper end of the sleeve is positioned adjacent or the counterbore 28of the rotorhub .and is tapered inwardly to provide an axial dischargenozzle 71. So long as this nozz'le'or opening is unrestricted, lacquerwillflow from the'tank tothe rotor for discharge from the latter.However, when no container is overlying the rotor, it is obviousthat nospraying be needed, and the lacquer flow wouldbe wasted.

Therefore, to permit a closing of this opening, and a control of lacquerflow, -I provide a needle valve 72 arranged to selectively open andclose the opening 71. The

valve is slidably carried within the sleeve 'by providing "the samewithaplurality ofribs 73 so as to 'permitaxial movement'without any lateraldisplacement. The lower endofithe valve is carried onan axiallyextending rod 74 which extends beyond the sleeve bottom foractuation-thereof. A packing 76 will be disposed between the sleevebottom and .the rodto"prevcnt filiquid leakage therebetween.

.Any suitable-means, either manual or automatic, .may be utilized tomove the rod for opening and 'closing of the valve, but I:prefer to usean automatic mechanism .under which :the valve will remain closed until'arcontainer .is inserted -=over the rotor at which .time;.the valvewill :open. This may be done as diagrammatically illustrated in FIGURE 1wherein a solenoid 81 having a plunger 82, normally extended, is securedto the rod 74. Actuation of the solenoid to retract its plunger andconsequently open the valve may be controlled by any suitable switchmechanism such as a first switch 83 arranged to be engaged by thecontainer to energize the solenoid, and a second switch 84 operativelyassociated therewith which will be engaged by the coated container uponreaching its lowermost position to deenergize the solenoid. Naturally,by virtue of the valve arrangement, pipe 66 is provided with a by-pass86 around the pump 69.

In FIGURE 4, a diagrammatic showing is made of a slight modification ofthe foregoing apparatus wherein a pair of rotors 91 and 92 are utilized,with each rotor turning in an opposite direction to the other. Thereason for such an arrangement is that with a single uni-directionalrotor it is possible that projections, such as rivets on the containersurface would not be fully coated, as the leading edge portion of theprojection (i.e., with respect to rotor rotation) can be left uncoated.Obviously the dual direction rotation of a pair of rotors would overcomethis possible source of difficulty.

For the foregoing description, both the apparatus and its mode ofoperation are believed apparent. In use, the lacquer in tank 61 is firstheated to a temperature just above the boiling point of the alcohol orother solvent contained therein. Motor 57 is actuated to effect rotationof the rotor and pump 69 is likewise operated. However, the needle valve72 will keep the opening 71 closed, so no lacquer will enter the rotor.However, when a container is lowered over the apparatus into the splashreceptacle, and switch 83 engaged, the solenoid Will move rod 74 to openthe nozzle 71 whereby lacquer under pressure will be forced through thesleeve bore, through opening 71, into counterbore 28, and through theports 41 to engage the baffle or deflector 43 for distribution in rotorchamber 34. The centrifugal force will impell the lacquer as well as thesolvent vapors towards the container surface, such vapors serving tosweep all air from the surface on which the lacquer droplets aredeposited. By then lowering the container, the entire surface will beuniformly and properly coated.

What is claimed is:

1. Liquid spray apparatus of the character described comprising a rotorincluding a hub and a flanged body extending radially outward therefromprovided with an annular surface portion having a relatively shallowsubstantially inverted frusto-conical configuration terminatingoutwardly in a raised continuous peripheral lip disposed in asubstantially single radial plane, passage means associated with saidhub disposed to supply liquid to inner peripheral regions of saidsurface to flow thereover and be uniformly discharged from said lip byrotational forces, a cover plate disposed in spaced relation above saidflanged body and defining therewith a chamber enclosing at least thearea bounded by said lip into which ingress of air is prevented, and anannular member provided with a plurality of perforations and disposed inspaced relation to and surrounding said peripheral lip of said annularflange surface portion and upon which liquid discharged from suchportion impinges and is expelled tangentially outward in a finelydispersed form substantially free of admixture with dispelled air.

2. Liquid spray apparatus of the character described comprising a rotorincluding an axially bored hub and a flanged body extending radiallyoutward therefrom provided with an annular surface portion having arelatively shallow substantially inverted frusto-conical configurationterminating outwardly in a raised continuous peripheral lip disposed ina substantially single radial plane, passage means communciating withthe central bore of said hub and including an annular groove overlyingthe bore to receive liquid therefrom and arranged to supply liquiduniformly to inner peripheral regions of said surface to flow thereoverand be uniformly discharged from said lip by rotational forces, a coverplate disposed in spaced relation above said flanged body and definingtherewith a chamber enclosing at least the area bounded by said lip intowhich ingress of air is prevented, and an annular member provided with aplurality of perforations and disposed in spaced relation to andsurrounding said peripheral lip of said annular flange surface portionand upon which liquid discharged from such portion impinges and isexpelled tangentially outward in a finely dispersed form substantiallyfree of admixture with expelled air.

3. Liquid spray apparatus of the character described comprising a rotorincluding an axially bored hub adapted to be attached to a hollow driveshaft and a flanged body extending radially outward therefrom providedwith a shallow frusto-conical annular upper surface portion terminatingoutwardly in a raised continuous peripheral lip disposed in asubstantially single radial plane inwardly of the edge of said flange,passage means communicating with the axial bore of said hub and arrangedto supply liquid uniformly to the inner periphery of said surface toflow thereover and be uniformly discharged from said lip by rotationalforces, a cover plate disposed in spaced relation above and coextensivewith said flanged body defining therebetween a chamber and preventingaxial ingress of air, and at least one annular screen member providedwith a plurality of perforations and disposed between said flange andcover plate spaced outwardly from and surrounding said peripheral lipand upon which liquid discharged therefrom impinges and is expelledtangentially outward in a finely dispersed form substantially free ofadmixed expelled air.

4. Apparatus as defined in claim 3 wherein said passage means includes aplurality of axially diverging passages communicating with the axialbore of said hub and terminating in an annular concave downwardlyoriented passage overlying the central portion of the upper surfaceportion of the body.

References Cited in the file of this patent UNITED STATES PATENTS1,939,364 Peebles et al. Dec. 12, 1933 2,085,765 Peters July 6, 19372,508,709 Goetchius May 23, 1950 2,668,080 Peebles et al. Feb. 2, 1954-FOREIGN PATENTS 302,980 Great Britain Dec. 24-, 1928 367,890 GreatBritain Feb. 29, 1932 911,116 Germany May 10, 1954 OTHER REFERENCES- TheProblems Conquered to Make Hot Spraying Successful (Bede), published inOrganic Finishing, January 1951, pages 1519.

Airless Spray Painting (Bede), Pamphlet published by Bede Products,Incorporated.

